scholarly journals EFFECTS OF LIGHT ON NORMAL RABBITS, WITH ESPECIAL REFERENCE TO THE ORGANIC REACTION

1926 ◽  
Vol 44 (4) ◽  
pp. 483-502
Author(s):  
Louise Pearce ◽  
Chester M. Van Allen
Keyword(s):  
Physical State ◽  
Marked Decrease ◽  
Organ Weight ◽  
Ultraviolet Rays ◽  
Constant Darkness ◽  
Organic Reaction ◽  
Constant Illumination ◽  
Organ Weights ◽  
Especial Reference ◽  
Concrete Form

An analysis has been made of the organ weights of normal rabbits exposed to a constant illumination having none of the shorter ultraviolet rays and of other rabbits kept in darkness for periods of 2 to 12 weeks. The environment of constant illumination was associated with a well marked decrease in the relative weights of most organs, and in certain instances this occurred when the organ weights of the controls were becoming increasingly large. There was also an associated effect of stabilization of organ weight. The majority of the organs of rabbits caged in constant darkness also showed a tendency toward decreased and stabilized weights, but these effects were less pronounced than in the rabbits caged under conditions of constant illumination. A notable exception to this general result was the weight of the liver which was markedly increased. The results of this experiment support the conception that there is a relationship between light and the physical state of the animal organism which may be expressed in the concrete form implied by the trend or direction of organ weight.

Direct effect of melatonin on the accessory sexual organs in pinealectomized male rats kept in constant darkness

1982 ◽  
Vol 95 (1) ◽  
pp. 87-94 ◽  
Author(s):  
Kazuhiko Shirama ◽  
Tetsuo Furuya ◽  
Yuji Takeo ◽  
Kiyoshi Shimizu ◽  
Kyutaro Maekawa
Keyword(s):  
Marked Decrease ◽  
Levator Ani ◽  
Tissue Level ◽  
Male Rats ◽  
Ventral Prostate ◽  
Constant Darkness ◽  
Levator Ani Muscle ◽  
Organ Weights ◽  
And Function ◽  
Coagulating Gland

Pinealectomized and sham-pinealectomized male rats were subcutaneously implanted with 2 cm silicone elastomer capsules filled with testosterone or dihydrotestosterone (DHT) and placed in constant darkness (DD) for 50 days. The data revealed that the sham-pinealectomized group treated with testosterone differed from the pinealectomized group, having lower weights of accessory sexual organs and levator ani muscle. Pinealectomy had no effect on organ and muscle weights of DHT-treated animals. Exposure of male rats to DD resulted in a marked decrease in weights of ventral prostate, seminal vesicle, coagulating gland and levator ani muscle and a decrease in plasma DHT levels. However there was no significant reduction in plasma LH, FSH or testosterone. Pinealectomy of the rats exposed to DD resulted in restoration of both DHT levels and accessory sex organ weights. Melatonin implants in pinealectomized males led to an increase in both testosterone and DHT levels, accompanied by a decrease in sexual organ weights. The data indicate that the anti-gonadal effect of the pineal gland cannot be completely mediated by melatonin and that melatonin and some unknown factors can act at the tissue level to reduce the size and function of the affected sexual organs.

scholarly journals EFFECTS OF LIGHT ON NORMAL RABBITS, WITH ESPECIAL REFERENCE TO THE ORGANIC REACTION

1926 ◽  
Vol 44 (4) ◽  
pp. 447-459 ◽  
Author(s):  
Louise Pearce ◽  
Chester M. Van Allen
Keyword(s):  
Physical State ◽  
Ultra Violet ◽  
Great Majority ◽  
Postmortem Examination ◽  
Constant Light ◽  
Normal Male ◽  
Constant Darkness ◽  
Organic Reaction ◽  
General Body ◽  
General Physical

A group of 50 normal male rabbits kept under conditions of constant light that had none of the shorter ultra-violet rays and another group kept in constant darkness for 2 to 12 weeks were observed clinically and subjected to postmortem examination for the purpose of determining the effect of these environmental conditions upon general body health and the weights of organs. A similar group of 50 rabbits caged in an ordinary animal room for the same period, and two groups of 40 and 20 rabbits respectively, which had recently been brought into the laboratory, served as controls. It was found that the general health of the rabbits was not impaired by the artificial light or the exclusion of light. The gain in body weight which occurred in all groups was especially marked in the case of those kept under conditions of constant light. The incidence of spontaneous disease recognizable clinically during the experiment was extremely low and of a mild character and did not obviously disturb the health of the animal. It was found at postmortem examination, on the other hand, that 59.3 per cent of the rabbits caged indoors, that is in the light, dark, or unaltered rooms, and 58.3 per cent of those recently brought to the laboratory had visible lesions of some kind. The great majority of these lesions, however, were of a slight grade, and none appeared to have any deleterious effects upon the general physical state of the animals.

THE EFFECT OF COLD ACCLIMATION ON THE SIZE OF ORGANS AND TISSUES OF THE RAT, WITH SPECIAL REFERENCE TO MODES OF EXPRESSION OF RESULTS

1958 ◽  
Vol 36 (2) ◽  
pp. 209-216 ◽  
Author(s):  
O. Heroux ◽  
N. T. Gridgeman
Keyword(s):  
Experimental Data ◽  
Body Weight ◽  
Special Reference ◽  
Cold Acclimation ◽  
Muscle Mass ◽  
Cold Adaptation ◽  
Organ Weight ◽  
Organ Weights ◽  
White Rats ◽  
Body Weights

In experiments in which two groups of animals of different mean body weight are compared, individual organ weights of the animals can be expressed as absolute weights, as fractional weights, or as absolute weights statistically regressed onto constant body weights. The second, and commonest, mode of expression involves the assumption that the part is directly proportional to the whole, and this is shown to be unlikely for all organs except the muscle mass. Practical as well as theoretical justifications for the use of regressed weights (which utilize the actual slope of the line relating the organ weight to the whole) are given.The experimental data are from white rats kept for 4 weeks in a warm (30 °C.) or a cold (6 °C.) environment. It is shown that cold adaptation had no effect on brain, genitals, and lung weights, but that it reduced the growth of muscle, pelt, fat, skeleton, spleen, and thymus, and that it hypertrophied the liver, intestine, kidney, heart, and adrenals. Apparently cold acclimated rats are smaller than the controls mainly because they have a smaller muscle mass.

scholarly journals ORGAN WEIGHTS OF NORMAL RABBITS

1926 ◽  
Vol 43 (6) ◽  
pp. 733-741 ◽  
Author(s):  
Wade H. Brown ◽  
Louise Pearce ◽  
Chester M. Van Allen
Keyword(s):  
Organ Weight ◽  
Organ Weights

The results of a second series of organ weight determinations on normal rabbits are reported and the values obtained are compared with those for the first series. Figures are also given which represent the results obtained by combining the two series of animals or from weight determinations made on 645 apparently normal rabbits selected from stocks used for various experimental purposes.

scholarly journals Determining organ weight toxicity with Bayesian causal models: Improving on the analysis of relative organ weights

2019 ◽  
Author(s):  
Stanley E. Lazic ◽  
Elizaveta Semenova ◽  
Dominic P. Williams
Keyword(s):  
Body Weight ◽  
Multiple Testing ◽  
Weight Ratio ◽  
Organ Damage ◽  
Organ Weight ◽  
Analysis Of Covariance ◽  
Toxicity Tests ◽  
Weight Changes ◽  
Organ Weights ◽  
Chemically Induced

AbstractRegulatory authorities require animal toxicity tests for new chemical entities. Organ weight changes are accepted as a sensitive indicator of chemically induced organ damage, but can be difficult to interpret because changes in organ weight might reflect chemically-induced changes in overall body weight. A common solution is to calculate the relative organ weight (organ to body weight ratio), but this inadequately controls for the dependence on body weight – a point made by statisticians for decades, but which has not been widely adopted. The recommended solution is an analysis of covariance (ANCOVA), but it is rarely used, possibly because both the method of statistical correction and the interpretation of the output may be unclear to those with minimal statistical training. Using relative organ weights can easily lead to incorrect conclusions, resulting in poor decisions, wasted resources, and an ethically questionable use of animals. We propose to cast the problem into a causal modelling framework as it directly assesses questions of scientific interest, the results are easy to interpret, and the analysis is simple to perform with freely available software. Furthermore, by taking a Bayesian approach we can model unequal variances, control for multiple testing, and directly provide evidence of safety.

Patterns of Body and Visceral Growth in Human Prenates with Clefts of the Lip and Palate

2001 ◽  
Vol 38 (4) ◽  
pp. 341-345 ◽  
Author(s):  
Meropi N. Spyropoulos ◽  
Alphonse R. Burdi
Keyword(s):  
Body Size ◽  
Cleft Lip ◽  
Cleft Lip And Palate ◽  
Population Sample ◽  
Growth Patterns ◽  
Organ Weight ◽  
Human Embryos ◽  
Control Group ◽  
Cross Sectional ◽  
Organ Weights

Objective: To address the hypothesis that human prenates with birth defects such as clefts of the lip and palate show growth patterns in which body size and visceral growth are aberrant for prenatal age. Methods: Body size and organ weight measurements were derived from a cross-sectional population sample of 167 legally donated human embryos that were representative of key periods in visceral organogenesis and growth. Measurements included those of overall body size (i.e., length and weight) and weights of major organs. Data were analyzed for two comparative (age-matched) groups consisting of 120 typical-for-age “control” and 47 specimens showing the three typical cleft types. Organ weight data for the entire cleft group and for each of the three cleft subgroups were compared with those of the control group. Results: Cleft specimens showed crown-rump body sizes that were within one standard deviation of the control group. Among the entire cleft sample, each of the organ weight values was generally consistent with the organ weights observed for the age-matched control group. When organ weights for the cleft group differed from the controls, with one exception, some organs showed either increased or decreased organ weights. One remarkable exception was with lung weights, which were reduced for each of the prenates across the three cleft types. Among the three cleft groups, fetuses with cleft lip and palate showed the highest percentage of organ weight discrepancies (i.e., smaller than expected) as compared with the group with cleft palate, which showed the lowest. Conclusions: Organ weight aberrancies were observable (whether increased or reduced weights), and such aberrancies were not apparent until approximately 24 weeks (fertilization age).

scholarly journals Determining organ weight toxicity with Bayesian causal models: Improving on the analysis of relative organ weights

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Stanley E. Lazic ◽  
Elizaveta Semenova ◽  
Dominic P. Williams
Keyword(s):  
Causal Models ◽  
Organ Weight ◽  
Organ Weights

Zebrafish visual sensitivity is regulated by a circadian clock

1998 ◽  
Vol 15 (5) ◽  
pp. 851-857 ◽  
Author(s):  
LEI LI ◽  
JOHN E. DOWLING
Keyword(s):  
Light Intensity ◽  
Circadian Clock ◽  
Dark Adaptation ◽  
Escape Response ◽  
Early Morning ◽  
Visual Sensitivity ◽  
Constant Darkness ◽  
Constant Illumination ◽  
Late Afternoon ◽  
Normal Light

We have recently developed a behavioral assay, based on the escape response of fish to a threatening object, to analyze quantitatively the visual sensitivity of zebrafish. During the course of dark adaptation, we measure the threshold light intensity required to evoke an escape response. Under a normal light–dark (LD) cycle, thresholds for both the cone and rod systems are considerably lower in late afternoon hours than in early morning hours. Over a period of 24 h, zebrafish are most sensitive to visual stimuli prior to light off and least sensitive prior to light on. Under conditions of constant illumination, this rhythm of visual sensitivity persists for several days but is gradually lost. In constant light (LL), the rhythm persists 1–2 days; thereafter, visual thresholds at all times of the day converge at a level similar to thresholds measured in late afternoon hours in control animals. In constant darkness (DD), the rhythm persists at least 5 days; thereafter, it dampens to a level about a half-log unit less sensitive to that measured in the late afternoon hours in control animals. These data suggest that visual sensitivity in zebrafish is regulated by an endogenous circadian clock which functions to decrease the visual sensitivity.

scholarly journals The variability of organ weight background data in rats

1993 ◽  
Vol 27 (1) ◽  
pp. 65-72 ◽  
Author(s):  
Ephraim Gur ◽  
Trevor Waner
Keyword(s):  
Organ Weight ◽  
Analysis Of Covariance ◽  
Sprague Dawley ◽  
Control Groups ◽  
Organ Weights ◽  
Concurrent Control ◽  
Fields Of Study ◽  
Sprague Dawley Rats ◽  
Background Data ◽  
Weight Data

The variability of organ weight data in a series of 5 control groups of Sprague-Dawley rats was studied. Differences in body weight and organ weight data were detected between the studies. Attempts to reduce the variability of organ weights by using analysis of covariance or organ to brain weight ratios were only partially successful. Factors which may influence animals under controlled conditions and result in variability between studies are discussed. It is concluded that caution is needed when considering the use of organ weight background data as a means of comparison. The findings are in agreement with other fields of study in toxicological testing, and emphasize the importance of using a concurrent control for the purpose of comparison of data.

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